1. Field of the Invention
The present invention is related to a surface mounting piezoelectric oscillator consisting of especially base print board and sub print board containing crystal oscillator disposed on the base print board.
2. Description of the Related Art
Piezoelectric oscillator which provides stable frequency signal is widely used as a clock source for communication devices and electronic devices. Small-sized Surface Mount Device (SMD) types are being manufactured more because of miniaturization of those devices and for corresponding high frequency. Also, the change of surrounding temperature causes several ppm frequency changes of the piezoelectric oscillator so that a piezoelectric oscillator with improved electric characteristic can be used frequently.
In order to minimize mounting space in a high density circuit format, a surface mounting piezoelectric oscillator disclosed in Japanese Unexamined Patent Application Publication No. 2000-252748 adopted the structure of two layers of a base print board and a sub print board which has a crystal oscillator on its top. Also, in order to minimize an effect of ambient temperature and to enhance stability of the oscillatory frequency of the piezoelectric oscillator, some of the piezoelectric oscillators have two layers of the sub print board with the crystal oscillator to avoid direct effect of temperature changes outside of the oscillator.
The surface mounting piezoelectric oscillator consisting of the base print board and the sub print board conducts electrically from an external terminal to the sub print board. Also, the sub print board is needs to be supported on the base print board. Therefore, the surface mounting piezoelectric oscillator has a metal strut that conducts electrically to the sub print board and supports it at the same time.
The piezoelectric oscillator disclosed in Japanese Unexamined Patent Application Publication No. 2000-252748 has a soldered metal strut fixed to the base print board. In order to avoid the solder which fixes the metal strut touching the circuit board where the piezoelectric oscillator is attached to, a reentrant hole is created on the side of the circuit board as a through-hole. However, the solder may short out with the circuit board through the through-hole which is a part of reentrant hole because the solder may melt and leak out by the heat created when a piezoelectric oscillator is mounted to the circuit board.
This invention addresses the above-mentioned problems. An aspect of the present invention provides a highly reliable piezoelectric oscillator such that solder melted by heat does not leak from the oscillator and also the solder put on the mounted circuit board does not come into the piezoelectric oscillator.